A magnetic bookmark contains two magnets installed on each flap of the bookmark that attract one another and essentially clasp a page of the book. In theory, any kind of magnet can be used; however, a bookmark has to be thin and not all magnets can be practically milled to such dimensions. Ferrite, the basic gray magnet found in a variety of items like refrigerator magnets, happens to be useful for magnetic bookmarks.

Ferrite Magnets
Ferrite or ceramic magnets are made out of a variety of chemical compounds based on iron oxide (Fe2O3). The actual general chemical formula for a Ferrite magnet is MO-6Fe2O3 where M stands for barium, strontium or any combination of the two. Ferrite magnets are generally formed through a compression or extrusion molding technique followed by sintering, a process of using pressure or heat below melting point in order to bond metal or metallic particles. These magnets can be further shaped by diamond grinding wheels.

Properties of Ferrite Magnets
Ferrite is said to be the least expensive of all magnetic material and has very good magnetic properties, making it very popular. Ferrite has relatively weak structural properties, which is both an advantage and disadvantage. Having a weak structure means Ferrite cannot be used in applications where magnetic equipment has to be placed under high stress, such magnetos, guitar pickups, instruments, medical devices and automobiles.

The weak structure of Ferrite also means it can be shaped into a great variety of forms. It can be easily pulverized into powder, and it is for this reason that Ferrite powder can be mixed with molten vinyl or other flexible polymers to manufacture flat magnets.

Applications of Ferrite Magnets
Ferrite magnets have a great number of household and industrial uses. Consumer-grade speakers make use of Ferrite or ceramic magnets. The common refrigerator magnets, either those that look like flat rubber sheets with prints or small plaster sculptures with disc-shaped magnets on the back, usually make use of Ferrite. Some lawnmowers and outboard motors also use such magnets.

Making Bookmarks Out of Ferrite Magnets
Store-bought magnetic bookmarks are made the same flat and flexible magnetic material used for some calendars or advertisement materials. A hobbyist, however, can use the same flat and flexible magnetic sheets as bookmarks using two pieces that would attract each other. These flat sheets can be easily cut to bookmark shape and size using a pair of scissors. Creative individuals may even stick or add some form of decoration to individualize their bookmark designs. If a flexible magnet is unavailable, a hobbyist can use two disc-shaped magnets extracted from old refrigerator magnets and attach them to bookmark shaped cutouts, making sure that the exposed side of the magnets have opposing poles.